Field of the Invention
The present invention relates generally to programmable controllers of the type used in industrial automation. More particularly, the invention pertains to an input/output (I/O) module connectable with a programmable controller.
Description of the Prior Art
A programmable controller is a type of general purpose industrial computer which controls the operation of industrial or factory automation equipment or processes, such as an assembly line or a machine tool, in accordance with a stored program. The stored program includes a series of instructions or commands that direct the programmable controller to execute actions.
One conventional type of programmable controller includes a rack that contains functional modules. A rack backplane provides signal buses and connectors for electrically coupling the functional modules. One functional module is a control module that has a processor which sequentially executes the control program stored in memory of the control module. Other functional modules include I/O modules that are provided to interface various input and output devices to the processor. The I/O modules are placed or inserted into the rack. The location of the I/O module in the rack typically defines the address to reference each connected device. Other known programmable controller systems allow the user to select or set the addresses for each module by setting internal switches.
Therefore, it is desirable to improve the module number selection to be well suited for rackless programmable controller systems, as well as provide ease of interchangeability of I/O modules and operator identification where the I/O modules are not preset by user selected switches or dictated by rack locations. As will be described in greater detail hereinafter, the system and method of the present invention accomplishes these tasks and employs a number of novel features that render it highly advantageous over the prior art.
Accordingly, it is an object of this invention to provide an improved I/O module for use with a programmable controller system.
Another object of this invention is to provide a method and system for assigning module numbers to I/O modules.
Still another object of this invention is to provide an I/O module that determines the direction of bus flow therethrough and contains a programmable module number.
To achieve the foregoing and other objectives, and in accordance with the purposes of the present invention, an I/O module is provided for use with a programmable controller system having a master controller serially connected to a plurality of I/O modules. Each of the I/O modules includes a programmable memory having a first memory address for receiving a module number and a second memory address for receiving a signal direction indicator. A module number signal line is operatively coupled with the memory. The module number signal line has a pair of inputs, either of the inputs being configured and adapted for receiving a module number signal across a signal line connected therewith. The other one of the inputs is adapted for propagation of the module number signal downstream. A logic circuit sets the second memory address with the signal direction indicator corresponding to the module number signal being received by a particular one of the inputs.
Other objects, features and advantages of the invention will become more readily apparent upon reference to the following description when taken in conjunction with the accompanying drawings, which drawings illustrate several embodiments of the invention.